What Does 5W-40 Engine Oil Mean?
1 Answers
5W-40 engine oil refers to the viscosity grade of the oil. Oil viscosity is the most important performance indicator for measuring the fluidity of oil under various conditions. Internationally, 'SAE' is commonly used to denote the viscosity grade of engine oil. Oil viscosity: Simply put, it indicates whether the lubricating oil is thin or thick. Lower oil viscosity means the oil film is thinner, with better fluidity and relatively less resistance to engine operation; however, it has weaker resistance to shear under high temperature and pressure. Conversely, higher oil viscosity means the oil film is thicker, with reduced fluidity and relatively greater resistance to engine operation, but it offers better shear resistance under high temperature and pressure, helping friction pairs resist wear under greater pressure. Therefore, most family cars focused on fuel economy use low-viscosity oil, while performance cars focused on power and trucks frequently operating under heavy loads mostly use high-viscosity oil. SAE: Internationally, 'SAE' is commonly used to denote the viscosity grade of engine oil. SAE stands for the 'Society of Automotive Engineers' in English. It measures values such as low-temperature starting viscosity, low-temperature pumping viscosity, high-temperature kinematic viscosity, and high-temperature shear viscosity of automotive engine oil. Based on the measured data, engine oil is divided into several grades, which constitute the SAE viscosity index of the oil.
